The present invention relates to a thermostat for cooling an engine, and particularly to a thermostat which can prevent blurring of the shaft of the piston.
At present, as commercially available cooling systems for engines, most of the systems are types which cool the engines by water-cooling. The water-cooled system prevents overheating due to the heating of the engine and prevents overcooling of the engine in cold times, always keeping the engine at an optimal temperature.
As shown in FIG. 6, in the cooling system by water-cooling, a radiator R is placed outside of an engine E, and the radiator R and the engine E are connected by means of a rubber hose, etc. to circulate a cooling fluid. The main configuration is composed of the radiator R, which plays a role as a heat exchanger, a water pump P, which forcedly feeds the cooling fluid from the engine E to the radiator R, a thermostat 1xe2x80x2, which controls the flow of the cooling fluid to or from the radiator R depending upon a change in the temperature of the cooling fluid to keep the temperature of the cooling fluid at an optimal level, and a rubber hose etc., which forms a circulation channel for the cooling fluid. When the cooling fluid is higher than a prescribed temperature, the thermostat 1xe2x80x2 feeds the cooling fluid, which has been cooled by the radiator R, to the engine E via a cooling fluid channel 3xe2x80x2. When the cooling temperature is lower than a prescribed temperature, as in the case of starting the engine E, the thermostat 1xe2x80x2 circulates the cooling fluid within the engine E via a bypass channel 3Axe2x80x2. Such a water-cooled system for cooling an engine is utilized in an engine for a two-wheeled vehicle as well as an engine for four-wheeled vehicle.
As shown in FIG. 6, from the time of starting the engine E to warming the engine E to an optimal temperature, the thermostat 1xe2x80x2 closes the cooling fluid channel 3xe2x80x2. In other words, the cooling fluid from the engine E does not goes toward the radiator R, but passes through the bypass channel 3Axe2x80x2 and circulates within the engine E (see the arrow in FIG. 6 (a)), which makes the temperature of the engine reach an optimal level within a short period of time. On the other hand, as shown in FIG. 6 (b), after the temperature of the engine E attains an optimal level, a valve element 12xe2x80x2 of the thermostat 1xe2x80x2 is opened (see FIG. 7), to thereby open the cooling fluid channel 3xe2x80x2 at the side of the radiator R. Then, the cooling fluid passes through the radiator R and circulates within the engine E (see the arrow in FIG. 6 (b)), keeping the temperature of the engine cooled down at an optimal level.
As shown in FIG. 7, in the conventional thermostat 1xe2x80x2, a guide portion 11xe2x80x2 of an element 10xe2x80x2 is not fixed by a supporting member, or anything else. and, thus, when a piston 16xe2x80x2 which is guided by the guide portion is extended, the piston 16xe2x80x2 sometimes extends in the state of blurring the shaft. If the piston 16xe2x80x2 is extended in such a state, there arises a tendency to wear the piston 16xe2x80x2 and the guide portion 11xe2x80x2 in a bias manner and a gap would occurs between the piston 16xe2x80x2 and the guide portion 11xe2x80x2. In addition, since the thermostat 1xe2x80x2 is placed in a manner that it is always soaked in the cooling fluid within the cooling fluid channel 3xe2x80x2, the cooling fluid is sometimes leaks into the gap formed between the piston 16xe2x80x2 and the guide portion 11xe2x80x2, and the dust and dirt existing in the cooling fluid sometimes penetrate into the gap.
As described above, if the piston blurs the shaft while advancing and retreating, it is liable to wear the piston 16xe2x80x2 and the guide portion 11xe2x80x2 in a bias manner, making it difficult to enhance the durability of the thermostat 1xe2x80x2.
An object of the present invention is, therefore, to provide a thermostat which can prevent the blurring of the shaft and which excels in durability.
According to the present invention, such an object is attained by a thermostat, which is placed in a cooling fluid channel of an internal combustion engine and which controls the flow of a cooling fluid within the cooling fluid channel depending upon a change in the temperature, said thermostat having
a cylindrical valve body having an inlet opening, an outlet opening, and a bypass opening formed on the circumference surface thereof and fixed at the position where said inlet opening and said outlet opening are communicated with the cooling fluid channel,
a fluid channel area which communicates said inlet opening with said outlet opening within said valve body,
a thermo valve having a piston which goes forward and backward according to the actions of a thermal expansion element within a thermal-sensitive member and the function of a spring member at one side, and having a valve element which moves forward and backward across said fluid channel area whereby said thermo valve slides within the valve body due to the movement of the piston, and
a bypass valve element which stands parallel to the movement of the piston at another side of said thermo valve and which can be inserted into a bypass channel;
said valve element opening or closing said inlet opening and said outlet opening due to the movement of said bypass valve element together with said piston to communicate or block said fluid channel area, and said valve element opening or closing the bypass opening and said bypass valve element opening or closing the bypass channel to communicate or block the bypass opening and the bypass channel.
According to the thermostat of the present invention, since the thermo valve having the piston and the bypass valve are unified with each other, the bypass valve moves forward or backward according to forward or backward movement of the piston. What is more, since the bypass valve is inserted into the bypass channel by the extension of the piston, the piston can extend without blurring of the shaft.